The goal of this project is to evaluate the toxicity of pentavalent (sodium metavanadate) and tetravalent (vanadyl sulfate) vanadium compounds, following exposure in drinking water. Two-week studies of both compounds have been completed recently; subchronic studies are currently being designed by NTP. Humans are likely to be similarly exposed to these compounds in drinking water. As there are little available toxicity data on these compounds, these short-term studies provide valuable data to design more definitive reproductive/developmental and chronic toxicity/carcinogenicity studies. In addition, the 2-week studies were designed similarly to allow comparisons of the toxicity between pentavalent and tetravalent vanadium. Keywords: toxicity, drinking water, vanadium, pentavalent, tetravalent, vanadyl sulfate, sodium metavanadate.